A clutch mechanism for automobiles is arranged between an engine and a transmission, and functions to transmit or interrupt output from the engine to the transmission and successive drive train components. In a manual transmission (MT), a flywheel is arranged on the engine side, a pressure plate is arranged on the transmission side, and a clutch disc having friction materials attached thereto is arranged therebetween. A diaphragm spring generates a spring force so as to cause the pressure plate to press the clutch disc against the flywheel. With this, a frictional force is generated, and power from the engine is transmitted. When the diaphragm spring is pressed, the clutch disc is separated from the flywheel, and the clutch is disengaged. A clutch release bearing device functions to press the diaphragm spring in order to disengage the clutch.
As illustrated in FIG. 7, a clutch release bearing device, which is collectively represented by the reference symbol “A”, is slid along a front cover 34 by a release fork 32 interlocked with a clutch pedal (not shown). The front cover 34 is mounted to a clutch case 36 of the transmission, and an input shaft 38 of the transmission passes therethrough. Normally, the clutch release bearing device A is separated from a diaphragm spring 40, and the diaphragm spring 40 functions to cause a pressure plate 42 to press a clutch disc 44 against a flywheel 46 so that a clutch is engaged. In this state, when the clutch pedal is depressed, the release fork 32 pivots in a counterclockwise direction in FIG. 7 so as to press the clutch release bearing device A against the diaphragm spring 40. With this, the diaphragm spring 40 is deflected, and the pressure plate 42 is separated from the clutch disc 44. In this way, the clutch is disengaged.
The clutch release bearing device A mainly includes a sleeve configured to slide along the front cover 34 in an axial direction, a ball bearing mounted to an outer periphery of the sleeve, a cover configured to integrally hold an outer ring of the ball bearing and the sleeve, and an elastic member interposed between the outer ring and the cover. The cover has a part configured to be hooked by the release fork 32. Then, when the clutch ball release bearing device A is moved toward the diaphragm spring 40 with the release fork 32, an inner ring of the ball bearing is pressed against the diaphragm spring 40, and is rotated together with the diaphragm spring 40 (inner ring rotating type).
In Patent Literature 1, there is disclosed a clutch release bearing device in which a separate contact member is press-fitted to the inner ring of the ball bearing, and the contact member is brought into contact with the diaphragm spring. In Patent Literature 2, there is disclosed a clutch release bearing device in which the inner ring of the ball bearing and the contact member are integrally formed of a steel plate. Note that, in each of the clutch release bearing devices, a contact position between the contact member and the diaphragm spring is arranged on a radially outer side with respect to an outer periphery of the inner ring.